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Many states have established targets to reduce greenhouse gas emissions by 50-80% by 2050. The federal government has also established a 2020 target of reducing carbon emissions by 17% (based on a 2005 base). These targets are based on limiting global temperature increases to 2°C. While much of the reduction in emissions will come from the electric utility sector, the transportation sector must also contribute significant reductions over this time frame.

The goal of this study was to examine various policy options that can achieve large-scale reductions by 2040, based on the current time frame of Annual Energy Outlook forecasts. Existing regulations on light-duty vehicle fuel economy and carbon emissions are leading to rapid decreases in emissions. New heavy-duty fuel economy standards will also soon take effect. These are supplemented by the renewable fuel standard. But these efforts are unlikely to be sufficient to meet what will be challenging reductions in greenhouse gas emissions in the next 30 years. This study examined the degree to which three key travel-demand policies—road pricing, directing new population growth to more compact areas, and increasing the level of transit service—could contribute to reductions within this time frame.

The VISION model was used to estimate current trends in greenhouse gas emissions. This model accounts for expected changes in population, technology, and fuel options based on existing regulations. The model was updated with the most recent carbon emission and fuel economy standards for light- and heavy-duty vehicles. It accounts for life cycle greenhouse gas emissions, mainly associated with upstream production of fuels.

To forecast the changes from the three policy scenarios, the California activity-based travel demand model was used. This is a statewide model that covers all the regions of California. From this model a variety of travel-demand elasticity estimates were derived for each policy option. These were then applied to forecasts of future vehicle miles of travel from the VISION model while also accounting for potential error bands inherent in the modeling process.

Results provide useful information for understanding the effectiveness of alternative policies and any additional regulatory policies that might be needed to close the gap. Of the three travel demand management policies analyzed, only the pricing policy comes close to achieving the 50% emission reduction target over the period from 2000 to 2040, and this assumes both a doubling of the price of driving and the highest range of elasticity estimates from the model. Transit and land-use policies provide only minor reductions in emissions. Overall, this analysis suggests that reductions of about 20% to 40%—in addition to those provided through demand management strategies—may be necessary to meet aggressive mitigation goals.

Medium- and heavy-duty vehicles, primarily freight traffic, achieve only small reductions in emissions even with the pricing scenarios. Freight emissions would not be affected by transit or land-use policies. This suggests that further technological improvements far beyond current regulations will be required to reduce emissions from these vehicles.

These results are not inconsistent with other “gap” analyses that have been conducted. Most studies conclude that both aggressive technology policies and reductions in travel demand are needed to achieve large reductions in transportation greenhouse gas emissions. This study reveals a potential gap, particularly in emissions from medium- and heavy-duty trucks, without further regulatory action. The need to increase the price of travel to reduce demand is also critical if the transportation sector is to contribute to global efforts to help stabilize temperatures at no more than a 2°C increase.

About Mineta Transportation Institutetransweb.sjsu.edu“The Mineta Transportation Institute (MTI) conducts research, education, and information and technology transfer, focusing on multimodal surface transportation policy and management issues. It was established by Congress in 1991 as part of the Intermodal Surface Transportation Efficiency Act (ISTEA) and was reauthorized under TEA-21 and again under SAFETEA-LU. The Institute is funded by Congress through the US Department of Transportation’s (DOT) Research and Innovative Technology Administration, by the California Legislature through the Department of Transportation (Caltrans), and by other public and private grants and donations, including grants from the US Department of Homeland Security.”

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